1. Field of the Invention
The present invention relates to an ink jet recording apparatus. More particularly, the invention relates to a circuit for supplying source power to a recording apparatus that effects recording with the provision of the power supply through a USB interface cable, as well as to a method for supplying source power.
2. Related Background Art
The power supply unit, which is mounted on the conventional printing apparatus, particularly on an ink jet printer, is generally provided with voltage (5 volts, for instance) for control circuit use, and voltage for driving circuit use to drive a motor or a recording head. Then, the voltage for the driving circuit use is further provided with two kinds of voltages, one for motor use and the other for recording head use. Thus, the three systems form the entire power supply structure. For some of the printing apparatuses, the motor voltage and the recording head voltage are commonly used to form the entire power supply structure by two systems.
As an interface used for these printing apparatuses, a parallel interface (that may also be called a centronics interface) that conforms to the IEEE1284 has been used in general.
In recent years, however, with the advancement in technologies to make the equipment smaller, and to provide a more effective operating system (OS) for a personal computer, a universal serial bus (USB) interface, which is capable of supporting the plug and play function, has been used more widely. For example, the Windows 98-OS produced by Microsoft Corporation, and the Mac-OS produced by Apple Computer Inc., among some other operating systems, support the USB interface as standard.
Whereas the conventional IEEE1284 interface comprises 8-bit data signal line, a plurality of control signal lines, and grounding line, the USB interface is a serial interface formed by D+, Dxe2x88x92 differential signal lines, 5-volt power supply line (power supply bus), and 4 grounding lines as shown in FIG. 1. In accordance with the USB specifications, the 5-volt USB power supply line (power supply bus) is regulated to supply electric power of maximum 5 volts at 500 milliamperes (hereinafter referred to as mA) from the host side, such as a personal computer, to a printing apparatus, such as a printer (which is defined as function by the USB terminology).
However, in order to provide the 500 mA, it is necessary to switch the power supply sources step by step in accordance with the designated communication protocol (which is performed at the time of bus enumeration). In other words, on the printer side, the low-power consumption status (the power value being 0.5 watts, the voltage value, 5 volts, and the current value, 100 mA or less) should be maintained, and then, by the bus enumeration control during this period, this is controlled and changed to the power status (the power value being 2.5 watts, the voltage value, 5 volts, and the current value, 500 mA or less) for recording operation due to the total power in demand.
Here, for the conventional printer, both the voltage for control circuit use and the voltage for driving circuit use are supplied from the DC power unit, which is generally provided inside the printer for its own use.
As a result, the conventional printing apparatus does not utilize the power from the USB power supply portion (USB power supply line) fully despite receiving the power supply from the USB power portion (USB power supply line). On the other hand, there is a problem at present that the power consumption of the printing apparatus should be made lower still, and the utilization of the power from the USB power supply portion (USB power supply line) should be taken into consideration as a subject to cope with the situation.
The present invention is designed to solve this problem. It is an object of the invention to provide an ink jet recording apparatus, which is provided with the control circuit that controls the recording operation using a recording head, and the driving circuit that drives the recording head, comprising the power supply portion of a serial interface to supply power to the control circuit with a first voltage value, and a second voltage output circuit for supplying power to the driving circuit with a second voltage value.
Another recording apparatus of the present invention, which is provided with a control circuit for controlling the recording operation using a recording head, and a driving circuit for driving the driving source to drive the recording head, comprises the power supply portion of a serial interface to supply power to the control circuit with a first voltage value, a power supply unit having a first voltage output circuit for supplying power to the control circuit with a first voltage value, and a second voltage output circuit for supplying power to the driving circuit with a second voltage value. For this recording apparatus, the power supply to the control circuit from the first output circuit and the power supply portion of the serial interface is executed in accordance with the status of the power supply portion of the serial interface.
The method of the present invention for controlling an ink jet recording apparatus, which is provided with a control circuit for controlling the recording operation using a recording head, and a driving circuit to drive the recording head, comprises the steps of operating the control circuit in the recording operation with the power supply from the power supply portion of a serial interface with a first voltage value, and operating the driving circuit by the power supply from the power supply unit with a second voltage value.